A pressure vessel for storing a fluid medium (such as hydrogen) typically includes a pressure chamber which contains the pressurized fluid medium that is moved in a controlled manner in or out of the vessel. In certain designs, the pressure vessel includes an inner plastic liner with two metal mouthpieces (bosses) arranged on opposite ends, and a filament wound outer shell to support the inner vessel liner.
Typically, the vessel liner is manufactured using a conventional injection molding, blow molding, rotational molding process, or thermoforming process. For example, the following patent documents describe a vessel liner (WO 1999/039896 Dulisse, JMK; WO 2007/079971 Wilier, Xperion; DE 19526154 Lange, Mannesmann etc.; and WO 1999/013263 Jensen, Raufoss), each of which is incorporated herein by reference in its entirety.
To permit controlled movement of fluids in or out of the pressure chamber, the vessel is typically configured with a pressure chamber orifice and a boss is fitted in the orifice. The boss is threaded or otherwise shaped for connection to nozzles, valves, gauges, tubes, and similar fixtures which direct and control fluid flow. Accordingly, the boss is formed of a metal or another conventional material having desired properties.
The boss typically includes a cylindrical neck with a longitudinal passage that provides fluid communication between the pressure chamber and the environment outside the vessel. In certain designs, the boss includes a shoulder portion secured to one end of the neck. The shoulder portion, which is larger than the pressure chamber orifice, is secured to the liner of the pressure vessel to militate against relative movement between the boss and the liner.
In application, a composite structure of the pressure vessel has to bear all forces. It is important to provide a smooth outer surface on the liner of the pressure vessel to guarantee the performance of the composite structure.
It would be desirable to develop a vessel liner and a method for manufacturing the vessel liner, wherein the vessel liner is formed having a substantially smooth outer surface.